Interferons are characterised as alpha class I, alpha class II, beta and gamma interferons as determined by inactivation of the antiviral effects with internationally accepted standard antibodies. Trophoblast-produced interferons are also, according to international rules, designated trophoblast interferons. A number of interferons derived from trophoblasts of non-human animals such as sheep and cattle, are known.
The known trophoblast interferons have been implied to be cytokines with an autocrine influence on differentiation of the normal trophoblasts, defence against virus infections, regulation of cell division and modulation of maternal immune attacks against the fetal tissues.
Several groups have demonstrated alpha interferon in amnion fluid, placenta tissue and cord blood, (Lebon et al. 1982,, DucGoiran et al. 1985, Chard et al. 1986) even from apparently uninfected term used placenta (Bocci et al, 1985). The cell(s) of origin and chemical composition except for neutralization by anti-interferon alpha antibodies was not delineated in these studies. Immunochemistry furthermore showed human trophoblasts to harbour alpha (Howatson et al., 1988). Earlier studies also showed animal trophoblasts capable of in vitro production of interferons (Godkin et al., 1982).
It had been reported that purified human villous trophoblasts isolated by negative selection (non MHC-1, A, B, C expression) may produce interferon in vitro. Term placenta trophoblasts were exposed to polyriboinosinic-polyribocytidylic acid (poly 1:C) which led to production of beta type interferon activity (Toth et al., 1990).
However, until the present invention, no interferon definitely shown to be produced by human trophoblasts had been isolated and characterized, and there was no indication that the interferons produced by human trophoblasts are different from known interferons.